Corrosion inhibitor



Patented Apr. 11, 1944 STTES CORROSION INHIBITOR Arthur C. Pabst, Douglaston, and John H. Prall, Lynbrook, N. Y., assignors to Socony-Vacuum Oil Company, Incorporated, a corporation oi New York No Drawing. Application April 28, 1942,

, Serial No. 440,888

22 Claims.

This invention relates to a corrosion inhibitor adapted to materially reduce the corrosive effect of aqueous liquid on metallic surfaces.

For many purposes aqueous liquids are maintained or circulated in contact with metallic surfaces. rosion and/or formation of scale are almost universally met within such cases and provision is generally made to reduce these eilects as much as possible. Among the varied uses of aqueous liquids to which this invention is applicable, the circulation of water in the cooling systems of internal combustion engines is important and may be'taken here as typical.

All commercial anti-freezes used in automobile cooling systems are aqueous solutions having freezing points sufficiently low to assure a full flow of the cooling medium under normal pumping or thermo syphoning conditions. The

most common anti-freeze are mono-, diand poly-basic alcohols, such as methyl, ethyl, isopropyl alcohols, ethylene glycol and glycerine mixed with water in such proportions as to produce the required freezing point depression. Aqueous solutions of inorganic salts are less widely used.

Considerable aeration of the coolant in the automobile cooling systems takes place because of the high velocity of circulation and shaking of the automobile in motion. The aeration contributes to the rapid rate of oxidation of alcohols, which in turn produces acidic materials corrosive. to the metals. The difliculty in finding adequate corrosion protection in automobile cooling systems lies in the variety of metals and alloys which come in contact with the coolant. Iron, brass, solder, aluminum and copper are the most commonly encountered metals. some inhibitors, for instance, are specific in protecting aluminum but do not exert the same action on iron, and vice versa. Experience has shown that soluble mineral oils containing a sulfonate and'soap emulsifier and nitrites represent about the best previously known all-purpose inhibitors for cooling systems containing a variety of metals.

We have discovered that nitrated fats represent a new group of materials admirably suited for the protection of multi-metal cooling systems. We have also discovered that nitrated fats are excellent inhibitors in water conditioning by which we mean a treatment of water for making it non-corrosive to the metalparts and free from deposition of scale.

ing is most commonly applied to water circulated in steel, cast iron and aluminum, other metals being encountered in the adjunct pumping equipment.

Nitrated fats, including methods for preparation and their efiects as lubrication assistants, are discussed in U. S. Patent No. 2,196,101, is-

Serious problems of surface cor-' Water condition-- desired, more extensive nitration.

iodine number of about 5 to 35, while preferred compositions have an iodine number of about 18. In general, the nitration should be suffi- -cient to improve alcohol solubility of the fat,

The method and to render it water dispersible. of nitration described in the above patent are applicable to the present invention, it being necessary, of course, to increase the proportion of nitric acid to raw fat in order to obtai n the LE I 7 Preparation of anti-freeze 0.5 per cent of nitrated tallow (18 I. N.) is

' dissolved in an alcohol blend consistingof 60% methyl alcohol and 40% isopropyl alcohol. For charging into an automobile cooling system, this mixture is further diluted with water using one part of inhibited alcohol blend and three parts of water.

Examrta II Preparation of a water conditioner Per cent by weight Nitrated tallow 18 I. N 1 Sodium olea 3 Borax 1 Water 86 Total Nitrated tallow and soap are melted and dissolved in a portion of hot water, borax is dis-. solved in the balance of water, and the two solution are combined into the finished product.

1.5 per cent of the above composition is sufficient to inhibit average New York city tap water. This amounts to 0.15% of nitrated tallow on the coolant. A correspondingly higher per cent of water conditioner may be necessary for harder water as is common practice with any water conditioner.

The emcacy of corrosion inhibitors for aqueous liquids can be readily demonstrated by experiments closely simulating the operating conditions in a cooling system of an. internal combustion engine. This test, while not published and recognized by technical societies such as A. S. T. M., has received wide acceptance by the industry. particularly in the evaluation 0t various water conditioners, hydraulic fluids and corrosion inhibitors. In this test, stainless steel racks holding test strips with metals usually encountered in cooling system, are half submerged in the liquid under test and refluxed for a period of 144 hours at 160 F. Upon completion of the test, the test strips are subjected to a standard procedure for removal of any traces of the product under test. The milligrams ofmetal lost, are a measure of the corrosiveness to any particular metal. The metals used in this test are as follows:

Cast iron (from an automobile cylinder head of a particular make) Aluminum alloy (from an automobile cylinder head of a particular make) Copper Brass Solder Fats, including both solid fats and fatty oils, in general, are suitable for the purposes of the invention when nitrated at least to the point where corrosion inhibiting properties are developed to a substantial extent. Preferably those fatshaving a relatively high iodine number are employed. This general class of inhibitors is capable of being dispersed n aqueous liquids generally encountered, including aqueous solutions of alcohols used in aqueous cooling media to reduce the freezing point. The proportion of nitrated fat is, as might be expected, dependent to a large extent on the nature of the aqueous liquid. Amounts from about 0.05% to by weight are efiective but for most purposes, about 0.1% to about 5% of the-inhibitor is used. In making up inhibited anti-freeze solutions, a 'comparable quantity of nitrated fat is used to provide the desired concentration upon dilution with water which is usually on the order of 1 part 4 anti-freeze to 3 parts of water. In general, antifreezes according to the invention will contain about 0.2% to about 20% of nitrated fat and the balance alcohol.

We claim:

1. An aqueous heat exchange liquid comprising a major proportion of water and a minor proportion of a water dispersible nitrated fat Metal loss, mans.

Water Inhibitor used AI umi- Iron mun Solder Brass Copper 1-1oo% N.Y O.tep -10s.7 -27.0 --7.0 +0.4 +0.4 2-100% N.Y 0 tap 6cc.hydrotonein600cc.ofwetcr +1.1 2.5 l.6 +0.4 --0.6 3-100%N.Y O.tap 1.5% water conditioner containing 10% 5.0 0.2 -6.2 --5.2 2.1

nitrated tallow (see Example II).

Nitrated fats show corrosion prevention effect on multi-metal systems when alcohol-water blends are used as coolants.

sufllcient. to substantially inhibit corrosion .of metals by said liquid.

2. An aqueous heat exchange liquid comprising Metal loss, ingms. Alcohol Water blerlid by Inhibitor used Al 1 v0 ume um Iron Solder Brass Copper Percent k," 1 476 N. Y. 0. tap 25 None -0. 9 -0. 8 None -0. 9 6-7B N. Y. O. 25 0.5% nitrated tallow... 2. 0 6. 8 1. 9 -2. 0 6-75 0 N. Y. 0. tap 25 Commercial preparation..---- -l. 2 10.0 -0. 6 -0. 3

The last line is representative of present comr'nercial antifreeze preparations being an inhibited product well received by the trade as an automobile anti-freeze. It will be seen that the nitrated tallow is on a par with the inhibitors in a satisfactory anti-freeze which is shown to contain an emulsified light oil and borax.

The following experiments prove that neither the. fat alone nor the nitro group in combination with another organic radical is effective as a corrosion inhibitor. 1

Metal loss, mgms. Alcohol Water blexlid by Inhibitor used A um vo ume Iron um Solder Brass Copper Per cent 775% N. Y. 0. tsp 25 0.5% common tallow 8l. 1 8. 8 -1. 6 -0. 2 -0. 5 875% N. Y. 0. tap 25 0.5% nitrobenzen 1L 9 10. 7 -2. 4 0.4 -0.6

a major proportion of water an'd about 0.15% of a water dispersible nitrated tat.

5. An aqueous. heat exchange liquid comprising a major proportion of water and about 0.5% of a water dispersible nitrated fat.

6. An aqueous heat exchange liquid comprising a major proportion of water and about 0.05% to about 25% of a water dispersible nitrated fat.

' 7. An aqueous heat exchange liquid comprising a major proportion of water and about 0.1% to about of a water dispersible nitrated fat.

8. An aqueous heat exchange liquid comprising a major proportion of water, a substantial proportion of alcohol and a minor proportion of a water dispersible nitrated fat sufiicient to substantially inhibit corrosion of metals by said liquid.

9. An aqueous heat exchange liquid comprising a major proportion of water, a substantial proportion of alcohol and a minor proportion of a water dispersible nitrated tallow sufiicient to substantially inhibit corrosion of metals by said liquid.

10. An aqueous heat exchange liquid comprising a major proportion of water, a substantial proportion of alcohol and a minor proportion of a water dispersible nitrated tallow having an dine number about 5 to 35 sufiicient to substantially inhibit corrosion of metals by said liquid.

' 11. An aqueous liquid comprising a major proportion of water, a substantial proportion of alcohol and about 0.15% of a water dispersible nitrated fat.

12. An aqueous liquid comprising a major proportion of water, a substantial proportion of alcohol and about 0.5% of a water dispersible nitrated fat.

13. An aqueous heat exchange liquid comprising a major proportion of Water, a substantial proportion of alcohol and about 0.05% to about of a water dispersible nitrated fat.

number about 18.

14. An aqueous liquid comprising a major proportion of water, a substantial proportion of alcohol and about 0.1% to about 5% of a water dispersible nitrated fat.

15. An anti-freeze intended for dilution with watercomprising a major proportion of a freezing point depressant and about 0.2% to about 20% of a water dispersible nitrated fat.

16. An anti-freeze intended for dilution with water comprising a major proportion of alcohol and about 0.2% to about 20% of a water dispersible nitrated fat.

17. An anti-freeze intended for dilution with water comprising a major proportion of a freezing point depressant and about 0.5% of a water dispersible nitrated fat.

18. An anti-freeze intended for dilution with water comprising a major proportion of alcohol and about 0.5% of a water dispersible nitrated fat.

19. An anti-freeze intended for dilution with water comprising a major proportion of a freezingpoint depressant and about 0.2% to about 20% of a water dispersible nitrated tallow.

20. An anti-freeze intended for dilution with water comprising a major proportion of alcohol and about 0.2% to about 20% of a water dispersible nitrated tallow.

21. An anti-freeze intended for dilution with water comprising a major proportion of a freezing point depressant and about 0.2% to about 20% of a water dispersible nitrated fat having an iodine number between about 5 and about 35.

22. An anti-freeze intended for dilution with water comprising a major proportion of a freezing point depressant and about 0.2% to about 20% of a water dispersible nitrated fat having an iodine ARTHUR c. PABST. JOHN H. PRALL. 

